The aim of these investigative studies is the continuation of research on various aspects of viral carcinogenesis with special reference to simian virus 40 (SV40). This undertaking has been pursued by the Principal Investigator for the past 13 years (l963-1976). In the immediate future the following phenomena will be investigated: (1) The relative role of the target (hamster) cell versus that of the viral (SV40) genome in determining morphogenesis and the differentiated state of SV40-induced neoplasms. (2) The importance of the presence of the viral (SV40) genome in the development and severity of oncogenicity in the SV40-hamster cell system. (3) The interrelationship of the various SV40-mediated cellular "neoantigens", and their significance in the persistence of the oncogenic state. BIBLIOGRAPHIC REFERENCE: Diamandopoulos, G. Th., Miller, M.H., McLane, M.-F. and Evans, P.G: Loss or persistence of the differentiated state of simian virus 40-induced hamster tumor cells before and after serial passage in culture. Cancer Res. 36: 3171-3177, 1976.